From DD-WRT Wiki
Munin is a simple tool for monitoring network devices such as Servers, Routers and Switches. It's a server-/client software enabling the client to monitor multiple servers (so called "nodes"). Beside the possiblity to install the server-software (munin-node) on a client for monitoring it, Munin is able to monitor by using SNMP which makes it interesting for DD-WRT routers.
 Installing Munin
Munin can not (?) run on DD-Wrt directly so we need an extra server which is online to the router every time. On this server we need
- a webserver such as apache
Please refer to the Munin-documentation how to initially set it up. Some good Howto's you find here:
- http://wiki.ubuntuusers.de/Munin (german)
- http://www.debuntu.org/how-to-monitoring-a-server-with-munin (english)
 configure Munin for DD-Wrt
To start monitoring our DD-Wrt device, we first need to enable SNMP in the Services-menu. Change the "Location" Name to a DNS-Name you can resolve in your network like "router" ("router" in my network is the DD-Wrt device which has IP-Addr "10.0.0.1"). After enabling the service, do not forget to apply the changes or reboot the router.
On the server running Munin:
- munin-node-configure --shell --snmp router | sh While "router" needs to be a DNS-Name for your DD-Wrt device. This will fail, if the DD-wrt device is not reachable by this name! In doubt, enter the name into your server's /etc/hosts file.
- open up /etc/munin/munin.conf and add
[router] address localhost use_node_name no
As the munin-node of your server is retrieving the SNMP-data, "localhost" is the correct address!
- In /etc/munin/plugin-conf.d/munin-node add
[snmp_router*] env.community public
This is required to let munin know which SNMP-connection parameter to use.
- now restart munin-node (/etc/init.d/munin-node restart), wait for at least 20mins and look at your munin-statistics. You now should see some traffic and load data of your DD-wrt device.